1. Field of the Invention
The present invention relates to a power transmitting part, a damper mechanism, and a flywheel assembly for transmitting rotary power.
2. Background Information
Various devices are installed in a drive train of a vehicle to transmit power generated by an engine. Examples of this type of device include clutch devices and flywheel assemblies. A damper mechanism is used in these devices for the purpose of damping rotational vibrations (e.g., see Japanese Laid-open Patent Publication Nos. 7-208547 and 9-242825).
This type of damper mechanism has, for example, an input member, an output member, a plurality of springs elastically connecting the input member and the output member in a rotational direction, and spring seats supporting end portions of the springs. In such a case, the input member and the output member are power transmitting parts.
In this damper mechanism, the input member starts to rotate with respect to the output member when power is transmitted to the input member. As a result, the springs are compressed between the input member and the output member and rotational vibrations are damped.
However, with conventional power transmitting parts, if a contact surface area between the input member and the spring seat is small, then surface pressure will become large and, thus, a spring seat made of resin will easily become worn. Meanwhile, if a large contact surface area is secured, then the weight of the input member will increase, which is not desirable.
In a conventional damper mechanism, a friction generating mechanism is provided to heighten vibration damping performance. The friction generating mechanism has a bush, a friction plate, and a cone spring. The bush is arranged such that it can rotate integrally with the input member. The friction plate is arranged such that it can rotate integrally with the output member. The cone spring is axially between the bush and the input member and pushes the bush and the friction plate against the output member. When the input member rotates with respect to the output member, the friction plate slides against the bush and generates a frictional resistance in a rotational direction. The frictional resistance causes a hysteresis to develop between the input member and the output member and damp rotational vibrations in an effective fashion.
In order to heighten the vibration damping performance of the damper mechanism, there is sometimes a demand to increase the hysteresis torque generated by the friction generating mechanism. However, if the effective radius of the friction member is increased, the friction generating mechanism will become larger in a radial direction, which is not desirable.
Meanwhile, a flywheel assembly has, for example, a first flywheel, a second flywheel, and a damper mechanism. The first flywheel is fixed to a crankshaft of an engine. The damper mechanism elastically connects the first flywheel and the second flywheel together in a rotational direction. A ring gear is fixed to the first flywheel to impart power to the crankshaft when the engine is started.
However, with a conventional flywheel assembly, it is necessary to machine an outer circumferential surface of the first flywheel because the first flywheel is fitted inside the ring gear and the manufacturing cost of the flywheel assembly tends to increase.
In this way, when positioning an annular member in a radial direction, it is not desirable to increase the amount of machining work because doing so induces an increase in the manufacturing cost.
Also, with a conventional damper mechanism, it is difficult to stabilize the operation of the spring seat because movement of the spring seat in a radial direction is not sufficiently restricted. When the operation of the spring seat is not stable, the vibration damping function of the damper mechanism is not stable.
However, with a conventional damper mechanism, if a contact surface area between the input member and the spring seat is small, then a spring seat made of resin will easily become worn.